1. Field of the Invention
Exemplary embodiments of the present invention relate to a semiconductor device and a method for fabrication thereof.
2. Discussion of the Related Art
With development of micro-processing technologies, complementary metal-oxide semiconductor (“CMOS”) technologies with improved frequency characteristics have been proposed. Applying semiconductor processing techniques makes fabrication of chips economically feasible. In particular, since immediate frequency (“IF”) circuits and digital circuits can also be integrated into a chip, a System on Chip (“SOC”) process is increasingly attracting attention as an appropriate technology for fabrication of single chips in the related art.
An RF-CMOS or bipolar/BiCMOS device includes an RF MOSFET, an inductor, a varactor, a metal-insulator-metal (MIM) capacitor and a resistor as major components. Here, the inductor is a single device occupying the greatest space in a chip and may be limited with regard to high frequency characteristics due to parasitic capacitance and resistance caused by an internal structure and/or constructional material thereof.
FIG. 1 is a top view illustrating a structure of an inductor 10; and FIG. 2 is a lateral cross-sectional view illustrating the inductor 10 taken along lines a-a′ shown in FIG. 1.
Referring to FIGS. 1 and 2, the inductor 10 includes a substrate 11, an interlayer oxide film 12 formed above the substrate 11, a metal part 13 placed on the interlayer oxide film 12, and a top protective film 14 enclosing the metal part 13 laminated on the interlayer oxide film 12. The metal part 13 constitutes an inductor line and has a spiral structure.
As such, the inductor 10 with a spiral structure may encounter a problem of reduced self-resonance frequency caused by parasitic capacitance generated between two metal parts 13 (d1) and/or between the metal part 13 and the substrate 11 (d2). When a frequency of a signal applied to the inductor increases, a cross-point (or an intersection) may be present at a position where inductance and capacitance are switched from each other and such a cross-point is referred to as “self-resonance frequency.”
For the spiral form inductor 10, when the inductance rises, the device structure is enlarged and a parasitic capacitance of the inductor is increased which in turn decreases the self-resonance frequency. Accordingly, an applicable frequency band of the inductor 10 may be reduced.